An astronomical telescope of ten fold angular magnification has a length of 44 cm. The focal length of the objective is
440 cm
44 cm
40 cm
4 cm
One face of a rectangular glass plate 6 cm thick is silvered. An object held 8 cm in front of the first face, forms an image 12 cm behind the silvered face. The refractive index of the glass is
0.4
0.8
1.2
1.6
A planoconvex lens is made of material of refractive index 1.6. The radius of curvature of the curved surface is 60 cm. The focal length of the lens is
50 cm
100 cm
200 cm
400 cm
Light travels through a glass plate of thickness t and refractive index μ. If c is the speed of light in vaccum, the time taken by light to travel this thickness of glass is
μtc
tc/μ
t/μc
μt/c
Time taken by sunlight to pass through a window of thickness 4 mm whose refractive index is is
2 × 10-4s
2 × 108s
2 × 10-11s
2 × 1011s
Colours of thin soap bubbles are due to
refraction
dispersion
interference
diffraction
The wavelength of light of frequency 100Hz is :
2 × 106 m
3× 106 m
4 × 106 m
5 × 106 m
A man is 6 ft tall. In order to see his entire image, he requires a plane mirror of minimum length equal to
6 ft
12 ft
2 ft
3 ft
A transparent cube contains a small air bubble. Its apparent distance is 2 cm when seen through one face and 5 cm when seen through other face. If the refractive index of the material of the cube is 1.5, the real length of the edge of cube must be :
7 cm
7.5 cm
10.5cm
Which of the following phenomenon is not common to sound and light waves?
Interference
Diffraction
Coherence
Polarisation
